Lazy generate an "AP" when an Annot's hidden state changes

core/fpdfdoc/include/cpdf_annot.h

 // Copyright 2016 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef CORE_FPDFDOC_INCLUDE_CPDF_ANNOT_H_
 #define CORE_FPDFDOC_INCLUDE_CPDF_ANNOT_H_
 
 #include <map>
@@ skipping 45 matching lines @@
                         CPDF_RenderContext* pContext,
                         const CFX_Matrix* pUser2Device,
                         AppearanceMode mode);
   void ClearCachedAP();
   void DrawBorder(CFX_RenderDevice* pDevice,
                   const CFX_Matrix* pUser2Device,
                   const CPDF_RenderOptions* pOptions);
   CPDF_Form* GetAPForm(const CPDF_Page* pPage, AppearanceMode mode);
 
  private:
+  void GenerateAPIfNeeded();
+
   CPDF_Dictionary* const m_pAnnotDict;
   CPDF_Document* const m_pDocument;
   const CFX_ByteString m_sSubtype;
   std::map<CPDF_Stream*, std::unique_ptr<CPDF_Form>> m_APMap;
 };
 
 CPDF_Stream* FPDFDOC_GetAnnotAP(CPDF_Dictionary* pAnnotDict,
                                 CPDF_Annot::AppearanceMode mode);
 
 #endif  // CORE_FPDFDOC_INCLUDE_CPDF_ANNOT_H_